Retainerless dental matrix and method of manufacture

ABSTRACT

A dental appliance for tooth matrix work comprising a unit consisting of a flexible metal band and a flattened metal lockloop anchored transversely adjacent one end of the band and the other end extending therethrough to form a circlet. One end of the band has a pre-coiled formation engageable by a rotatable winding member inserted into the inner convolution of said formation for winding the band to draw the circlet into tight conforming engagement about the tooth. The winding member may be removed from the tightened band, without loosening the band due to impregnating ridges of the lock-loop digging into and creating indentations in the tightened band, thereby locking and holding the band tightly around the tooth. For removal of the band, the lock-loop is easily severed and opened.

United States Patent [191 Lazarus [451 Nov. 25, 1975 RETAINERLESS DENTAL MATRIX AND METHOD OF MANUFACTURE [76] Inventor: Harry J. Lazarus, 36 Knox Lane,

Englishtown, NJ. 07726 [22] Filed: July 26, 1973 [21] Appl. N0.: 382,833

[52] U.S. Cl. 32/63; 32/63 [51] Int. Cl. A61C 5/12 [58] Field of Search 32/63, 40 R; 242/74 [56] References Cited UNITED STATES PATENTS 2,508,651 5/1950 Pratt et al. 242/74 3,411,214 11/1968 Lazarus 32/63 Primary ExaminerLouis G. Mancene Assistant Examiner.l. Q. Lever [5 7] ABSTRACT A dental appliance for tooth matrix work comprising a unit consisting of a flexible metal band and a flattened metal lock-loop anchored transversely adjacent one end of the band and the other end extending therethrough to form a circlet. One end of the band has a pre-coiled formation engageable by a rotatable winding member inserted into the inner convolution of said formation for winding the band to draw the circlet into tight conforming engagement about the tooth. The winding member may be removed from the tightened band, without loosening the band due to impregnating ridges of the lock-loop digging into and creating indentations in the tightened band, thereby locking and holding the band tightly around the tooth. For removal of the band, the lock-loop is easily severed and opened.

10 Claims, 25 Drawing Figures US. Patent Nov.2 5, 1975 Sheet1of3 3,921,299

Sheet 2 of 3 3,921,299

US. Patent Nov. 25, 1975 US. Patent Nov. 25, 1975 Sheet30f3 3,921,299

FIG. 18 PRIOR ART Flaw RETAINERLESS DENTAL MATRIX AND METHOD OF MANUFACTURE BACKGROUND OF THE INVENTION In regard to many types of inventions which represent a marked improvement over the prior art, it frequently is found that further improvements are either necessary or desirable, especially as use of the invention progresses. The improvements comprising the subject matter of the present invention are no exception in view of the same being improvements over the basic structure of applicants prior US. Pat. No. 3,411,214, issued Nov. 19, 1968. Said improvements are submitted to be meritoriuous, especially in the general areas of resistance of the band to tearing and undesirable deformation of said band, ease of manufacture, comfort to the patient, greater ease in applying and removing the matrix band to and from a tooth, safety to the patient, and ease of manipulation of the band, especially in removing the same, following the plugging of amalgam into a prepared cavity of a tooth to which the band has been applied.

In reconstruction of carious tooth surfaces, a tight anatomically self-contouring matrix band ideally is required. This is particularly true at the interproximal, gingival and subgingival portion of the tooth to be rebuilt or restored. The matrix acts as an anatomical tooth-encircling retaining wall for the amalgam that replaces and restores the carious surfaces of a tooth to its original anatomy. These surfaces are restored with silver amalgam or other suitable material which is plugged or forced into open and cleansed cavities while the plugging material is malleable. This anatomically formed matrix retains the shape of the restorative material until the same hardens, usually in minutes. Thereinafter, the matrix is opened and removed from the tooth.

While contoured matrix bands are known in the prior art, they have been subject to numerous disadvantages. For example, bands of this type have required a tightening and retaining tool or the like to apply and hold them in position after they are placed on the tooth. Said retaining tool remains attached to the matrix and this undesirably and awkwardly projects several inches from the mouth until the restorative work has been completed, as described hereinafter. One example of a typical conventional tool of this type comprises the subject matter of US. Pat. No. 2,502,903, dated Apr. 4, 1950, and a number of similar earlier patents.

Such projecting tool offered considerable obstruction and was cumbersome, especially in the event more than a single restoration was to be undertaken at any single appointment for a patient, as for multiple restoration work on more than one tooth. The projecting tool and handle considerably interferred with the operation of a dental plugging tool incident to filling said cavities in one or more teeth of a patient.

For many years, conventional matrix bands of the prior art type mentioned above have been applied around teeth by means of tightening and clamping tools which are of the order of between two and three inches long.

Tools of the type exemplified by the latter patent have been standard in dental practice for many years. No appreciable improvement thereover was introduced to the dental profession until the advent of the matrix band comprising the subject matter of applicants prior 2 US. Pat. No. 3,41 1,214. It was necessary when clamping conventional matrix bands by means of the tool illustrated in US. Pat. No. 2,502,903 that the tool remains connected to the band and projected outwardly from the tooth to retain the matrix band thereon.

In contrast to the foregoing conventional tool and its resultant problem of projecting from the oral cavity, the applicant also devised a special tool comprising the subject of his companion US. Pat. No. 3,435,905, is sued Apr. 1, 1969. This tool is designed to operate in combination with applicants invention. Its function is described hereinafter. Said special tool is designed in combination with matrix features to lock the matrix tightly about the tooth. After tightening and locking of the matrix has been accomplished, said tool is disengaged from the matrix by a counter-rotational winding of the tool to release the same from the coil and thus be removed from the matrix and the mouth. Thus, no objectionable obstruction in the operative field occurs. Such freedom from obstruction provides both a convenience to perform the necessary operation in the oral cavity and also offers the practitioner the opportunity to effect multiple restorations at one sitting of the patient as the tool is no longer present in the mouth.

The presence of the conventional retaining tool in the mouth is very disadvantageous. For example, such a retainer will lie across interproximal surfaces, thus, preventing insertion of wedges where said retainer lies across said surface and also interferes generally with other operations on the tooth as said tool clutters the operative field and blocks vision therein. The presence of the retaining tool in the mouth also restricts the space for manipulation and maneuvering necessary in doing other necessary dental operations in the mouth. In addition, bands used before applicants prior patent, have prevented the dentist from working on more than one tooth at a time.

While some matrix bands have been provided heretofore which are retained operatively upon a tooth without the presence of a retaining tool, these have generally been very unsatisfactory in practice, due to a lack of adapting and locking means. Adaptation of such matrices to a tooth also is poor. Such matricies are of cylindrical formation and are large enough to enable said matrix to slip over the large occlusal surface of the conical walls of a tooth. However, because the tooth is conical in formation and the matrix is not, the result is a poorly fitted matrix at the smaller gingival portion of the conical tooth, where the adaptation of the matrix to the tooth needs to occur.

Arcuately cut matrix bands also have been used because it is not feasible with many tooth formations to tighten a straight band sufficiently to conform it to teeth which are all, in varying degrees, conical in formation, without the banding material fitting loosely at the sub-gingival. Thus, a straight band will result in a non-anatomical restoration of areas of the smaller diameter of the tooth.

It is essential in restorative dentistry that all restorations make positive contact with abutting teeth. This necessitates restoration of the former contact points between adjacent teeth. If the contact point is not restored, the resulting space pennits the passage of food between adjacent teeth and into the interproximal gingival tissue, which may eventually result in peridontal disease. Such space can also cause undesirable movement or shifting of teeth that would otherwise hold against eventual movement from their position as when 3 such contact is reestablished by contact points of completed restoration. Such movement creates undesirable malocclusion requiring extensive and expensive corrective measures.

As practiced heretofore, a dentist attempted to make such contact of adjacent teeth by burnishing the matrix band to the adjacent tooth, but this provided only limited success, due to the difficulty of burnishing and successfully stretching a straight-sided matrix over to, and in contact with, the abutting adjacent tooth.

Furthermore, matrix bands embodying the principles of applicants prior US. Pat. No. 3,411,214, have included loop members through which the band may be drawn around a tooth. However, such loop members also have been less than ideal since they are not selflocking and, additionally, do not fully open for freely unrestricted removal of the matrix. This often caused fracturing or breaking the marginal ridges or edges of a newly placed filling in the tooth, which is still semi-soft and vulnerable to such fracturing.

Conventional matrix bands require substantial torque to adapt the same to a tooth. Applying such torque has developed a heavy-handed habit in practitioners who have a tendency toward excessive rotational winding of existing tools employing rotatable screws to attempt to tighten such conventional bands around a tooth. This results in excessive winding of the screws of existing tools which often results in stretching the portion of the matrix which extends beyond the tooth and is engaged within the mechanism of the tool. The portion of the matrix being stretched only partially effects limited adaptation of the matrix to the tooth, which is inadequate to prevent extrusion of the plugging material. Even though applicants matrix band of his prior patent required only a slight rotation and torque to adapt it to a tooth, said prior band could be ruptured by a said heavy-handed practitioner.

The winding of the coil of applicants matrix forms a tightly wound solid mass within which no stretching occurs, such as referred to above in existing matrices and techniques.

SUMMARY OF THE INVENTION The principal object of the present improved invention over that of applicants prior patent is to provide a matrix which is designed to afford a tight sub-gingivally fitted adaptation which, when locked fast to the tooth, produces an anatomically formed restoration upon completion of plugging of the amalgam.

Another object is to prevent the locking torque forces that are applied to adapt the matrix to a tooth from causing any destruction to the matrix before its usefulness is fulfilled due to any undue intraoral tightening of the matrix as heretofore referred to.

A further object is to obtain an immobile, intimate anatomical contact of the matrix on the sub-gingival portion of the tooth, with no undesirable spaces between said matrix and said tooth, so as to prevent plugging material from extruding under the pressures being applied to the restorative plugging materials.

A still further object of this invention is to provide, as in applcants prior patent, an anatomically adaptable matrix band having a curved arcuate section which comprises the encircling portion of the matrix and takes the form of a conical shape, the smaller end of this conical configuration being applied to the gingival portion of the tooth but the tightening of said section 4 around a tooth being accomplished by improved precoiling means that results in greater patient comfort.

A further object of the invention is to provide means to hold the band in circular formation for application to a tooth and comprising an improved lock-loop, formerly called a bridge in applicants prior patent, which is arranged to cooperate in effecting self-locking of the matrix band when tightened about the tooth, and is made of material that is substantially thicker and thus, an improved feature, as later herein described, to provide tear-resistance to certain portions of the band while being of relatively soft material to facilitate cutting the same at the time the matrix is to be removed from the tooth.

Still another object of this improved invention is to provide a pair of cooperating tear-resistant notches in the matrix blank for holding and positioning the lockloop on the matrix, as well as to provide clear visibility for the dentist and accessibility to the cutting area of the lock-loop.

Yet a further object of the improved invention is to provide a matrix band on which one end is wound into a pre-formed coil which is contoured to facilitate entry of an improved coil-winding member which may now more easily be inserted into the coil and the coil-winding member more reliably engages the leading edge within the coil to wind the band into tight conforming relation around the tooth.

Still another object of the invention is to continue, as in applicants prior patent, to provide in a matrix band, an automatic self-locking arrangement which will retain the tight fit of the matrix band around the tooth and which does not need any attention whatsoever by the dentist and wherein the dentist may remove the winding tool without interfering or disrupting the automatic self-locking of the band around the tooth.

Still a further object of the invention is to provide a matrix band with an improved lock-loop anchorage which prevents the notch which holds the lock-loop from being drawn therethrough and which, if it occurred accidentally, as when used by a heavy-handed dentist, would tear the lock-loop positioning ear and destroy the effectiveness of the band.

One further object of the invention is to form an improvement in the lock-loop by forming the same from considerably thicker material than in applicants prior patent, said increased thickness providing a bearing surface which is frictionally engaged by the spiralling coil of the band incident to the same being additionally coiled to tighten the loop of the band around a tooth, such frictional engagement serving to force that portion of the band which is under the coil and adjacent the lock-loop to move in a direction to form a locking shoulder due to the pressure of the coil against the matrix band and prevents the destruction of the lower lock-loop anchoring notch in the matrix by preventing the anchorage for the lock-loop from being drawn through the lock-loop and torn in the process.

It is still another improvement of the invention to provide a taper notch, similar to that in applicants prior patent, which extends inward from one edge of the coiled end of the matrix band, said notch being spaced a predetermined distance from the terminal end which is coiled. Whereby when said end is coiled, the portion extending between the notch and the terminal end, when coiled, extends in reverse spiral direction to the convolutions of the spiral coil which surround it, and being tapered along one edge, provides an improved engageable tapered leading edge within the socket in the inner core of said coil and also defines a strut extending diametrically across said socket within the coil and thereby controls the ID of the coil to assure engagement thereof by a coil winding tool, even under pressure of the entry of the said conical winding tool.

It is a further object, ancillary to the foregoing object to dispose said tapered leading edge located just inside the first spiral winding within the socket in said core in a manner to provide a sloping surface, which is adapted to be engaged effectively by uni-directional ratcheted teeth on the head of an improved conical winding member that engages the coil to wind and tighten it to adapt the matrix closely sub-gingivally about the tooth with all surplus banding material having been withdrawn by the rotating coil, such movement of the matrix into the sub-gingival region being automatic.

It is another object of the invention to provide on the band. adjacent one end, a projecting finger having a positioning notch in the outer end thereof for receiving a bight, or bent portion, of the lock-loop and the opposite or gingival edge of the band having a cooperating notch which receives the bight or bent gingival portion of the lock-loop, said notches together preventing any movement of the lock-loop from any undesirable displacement, either laterally or longitudinally, upon the matrix band.

One further object of the invention is to provide an inwardly and downwardly sloping, non-projecting edge along one side of the finger upon said band to provide clearance for the operative head of a winding member when the same is inserted into the core of the coiled end of the matrix band to wind and increase the coil and thereby draw off all surplus banding material from around the tooth and thus develop a close anatomical adaptation of the matrix to the sub-gingival of the tooth.

A still further object of the invention is to provide an improvement over applicants prior patent with respect to the unidirectional ratcheting tool head which has a conical angle that is greater than that of the conical socket in the core of the preformed coil, which assures a positive contact of the tool head with the core at least at one point when said tool head enters said socket, whereby rotation of the tool head relative to the core causes ratchets on the tool head to engage an improved sloping leading edge inside the coil core, said tool head having a non-faceted, smooth surface upon the truncated tip thereof, the periphery of said tip being chamfered to the root of said ratchets to produce a smooth end, unencumbered by any projecting edges which could catch upon any of the coil windings when inserting the tool into the coil core.

It is a still further object of the invention to provide the winding tool head with uni-directional teeth that, when rotated in a direction opposite to the coil winding direction, it is automatically released from its previous locking engagement within the walls of the core of the coil and thereby facilitate removal of said head of the winding member from the coiled portion of the band after the band has been fully installed upon a tooth.

Still another object of the invention is to provide a small hole in the band preferably adjacent the finger thereon and near the occlusal edge of the matrix band when applied to a tooth, whereby at the time the band is to be removed from a tooth, a hook-like tool can be inserted through the hole and thereby facilitate the opening of the matrix to effect the removal of the 6 opened band from the tooth without triggering or otherwise causing a fracturing of the new and still semisoft restoration.

It is another object of the invention to form the lockloop in an improved manner comprising an overlapping of the outer leg thereof onto the upper end of the inner leg at the topmost section of the finger to enable capturing said overlapped peices which are cut from the loop at the time removal of the band from the tooth is desired, said overlapping end of the outer leg extending through the notch in the finger, which also is partially sheared off at the time of removing the band from the tooth by severing the entire overlapped section of the outer leg of said loop.

It is a further object of the present invention to capture all of said removed pieces of lock-loop and ear within a compartment in a specially designed snipper designed for use with the matrix of the present invention, to avoid said severed pieces from flying into the oral cavity and perhaps down the patients throat, whereby the remaining portion of the lock-loop comprises a U-shaped configuration which remains in position over the gingival portion of the matrix band and is removed with the released matrix.

A still further object of the invention is to taper the end of the straight section of the matrix blank which is coiled in manufacture whereby when it is coiled, a concabe configuration is formed in the end of said coil which is disposed nearest the gingival tissue surrounding a tooth around which the loop of the band is to be mounted and thereby prevent the inner coil winding from being projected into said tissue during the coil winding operation, thus, avoiding trauma to the patient.

It is still another object to provide an additional taper on the improved end of the straight section which is formed into said pre-wound coil and thereby form an inverted cone at said top end of coil to afford easy entry of the winding tool head by guiding the leading end of said head substantially automatically into the central core of the coil.

For an understanding of the principles of the present invention, reference is made to the following description of typical embodiments thereof as illustrated in the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the improved matrix band blank which embodies the present invention.

FIG. 2 is a fragmentary perspective view of the lockloop end of the matrix band shown in FIG. 1, upon which a locking loop is mounted within notches of the blank shown in FIG. 1, said figure also showing an improved finger arrangement associated with said improved locking loop and a tool receiving hole to facilitate removal of the band from a tooth to which a filling has been applied.

FIG. 3 is a perspective view of the improved lockloop shown in FIG. 2, as seen on line A-A thereof, applied to a fragment of the band.

FIG. 4 is a perspective view illustrating an exemplary assembled band as supplied to the dentist with the preformed coil arranged to be applied to a tooth before tightening said coil, and also showing a dental winding tool in position to be inserted into the coil of the matrrx.

FIG. S-A is a diagrammatic plan view of an exemplary conventional spiral coil winding as used in appli- 7 cants prior patent.

FIG. -B is a view similar to FIG. 5-A but showing the improved reverse winding of the coil which provides a transverse strut in accordance with the present invention.

FIG. S-C is an exemplary, partially exploded, perspective transparent view showing the matrix being held in mechanism for forming the pre-coiled end of the matrix in accordance with the present invention.

FIG. 6 is a fragmentary, perspective view illustrating the bends and reverse direction taken by the tapered end formation of the coiled portion of the matrix as it is formed when pre-wound in the housing mechanism of FIG. 5, said formation providing a strut in the core of the coil and a sloping leading edge for winding tool engagement.

FIG. 7 is an enlarged fragmentary, semi-transparent, perspective view, in which the coiled end of the matrix is further wound that in FIG. 6 and the innermost convolutions of said coiled end of the matrix are clearly illustrated to show the sloping interior leading edge resulting from the reverse formation of said coiled end.

FIG. 8 is a fragmentary, translucent, perspective view, showing the head of a ratcheted conical coiling tool in process of being inserted into the coil core, the opening of which has a concave configuration.

FIG. 9 is a sectional view of FIG. 8, as seen on line B-B thereof, and showing the engageable leading edge of the coiled end of engagement by the winding member and also showing the contour of the strut and the concave configurations on the upper and lower portions of the coil.

FIG. 10 is a fragmentary perspective view of the coil winding head of the coiling tool showing the uni-directional conical ratcheted and engaging teeth and the smooth-faced truncated tip, the ratchets being helically arranged on the tool.

FIG. 11 is a fragmentary perspective view of an alternate winding head on which all of the facets are in straight line formation with the axis of the head.

FIG. 12 is an enlarged fragmentary perspective view of the tool head shown in FIGS. 10 and 1 l and illustrating the chamferred ends of the flutes which extend to the roots of said flutes.

FIG. 13 is a perspective view partially broken away to show details and illustrating the ratcheted winding tool head engaging the leading sloping edge within the socket of the pre-coiled end of the matrix, said figure also illustrating the preferred uni-directional winding of the pre-coiled end by the winding tool head to tighten the matrix upon a tooth and also showing how disengagement of the head from the leading edge within the coil core may occur by a reverse winding of the tool.

FIG. 14 is a transverse sectional view, as seen on the line CC of FIG. 13, illustrating automatic locking action produced by the lock-loop of the matrix.

FIG. 15 is an enlarged vertical sectional view, as seen on line DD of FIG. 13 and showing the impregnation of the matrix by the sharp ridges of the lock-loop.

FIG. 16 is a perspective upturned view illustrating the locking ridges of the lock-loop digging into the band and thereby locking the matrix to the tooth and also showing improved details of the thicker lock-loop to produce an offset locking shoulder in the matrix, said view taken from the edge of the matrix nearest the gingival of the tooth and a coiling tool being illustrated fragmentarily.

FIG. 17 is a transverse view of the matrix on the tooth, as seen on the line E-E of FIG. 16 and showing the matrix on the tooth in a partially tightened condition in which a space is shown between the band and the tooth at a point directly beneath the formed coil.

FIG. 17-A is a transverse view similar to FIG. 17, but showing the matrix fully tightened on the tooth and further showing the direction of movement of various portions of the matrix incident to being drawn tightly around the tooth and closing said space shown in FIG. 17 as a result of employing a thicker lock-loop.

FIG. 18 is a diagrammatic end view of a matrix in accordance with applicants prior patent.

FIG. 19 is a fragmentary, perspective view of the operative end of a pair of nippers having a transparent shield of the type preferred to be used incident to severing part of the locking-loop to permit opening and removing the matrix from a tooth, at the completion of performing a filling operation, to capture the severed segments within the shielded compartment to prevent escape thereof into the oral cavity.

FIG. 20 is a fragmentary plan view of the safety tips at the outer end of the blades of the nippers shown in FIG. 19 to prevent the accidental cutting of tissue.

FIG. 21 is a fragmentary perspective side elevation showing a series of teeth, the central one having a matrix embodying the principles of the present invention looped around the same and secured in tightly wound and locked condition, said matrix also showing generally an exemplary line of severance across the upper end thereof similar to that shown in FIG. 22.

FIG. 22 is a fragmentary, slightly exploded side elevation of the nippers shown in FIG. 19 following the snipping of the outer end of the locking loop from a matrix which is illustrated in perspective and also showing the line of severing across the upper end portion of the locking loop and the cut segments captured within the transparent shield.

FIG. 23 is a persepctive, slightly exploded view illustrating the severed segments of the locking loop which are to be captured within the nipper shield enclosure and also showing the matrix in process of being opened and removed from a tooth by a hooked dental tool, shown fragmentarily, in operative engagement with a hole formed in the matrix for that purpose to disengage the gingival notch of the matrix from the locking loop and permit the springing of the matrix to an open position while the remaining U-shaped segment of the lockloop is frictionally attached to the matrix for removal therewith from the tooth.

FIG. 24 is a fragmentary perspective view of the terminal portion of the arcuate end of the matrix from which the severed lock-loop has been removed to illustrate the offset shoulder and also to show the width of the terminal top in relation to the width of the adjacent notch.

DETAILED DESCRIPTION Reference will first be made to the matrix as it is finally assembled and seen in FIG. 4. Also seen in FIG. 4, is the dentists winding tool that said dentist uses to activate the mechanism of the disposable matrix band in FIG. 4. Said matrix winding tool is one of the applicants prior patents, this being US. Pat. No. 3,435,905, patented Apr. 1, 1969, to Harry J. Lazarus. For clarification of the function of the portions and components of the matrix and the matrix winding tool, references now will be made as to the application of said improved matrix and improved winding tool as provided in this application.

The fully assembled matrix 59 with its preformed coil 36 and the automatic locking loop 61 as shown in FIG. 4 is placed on a tooth for the purposes of restoring a caried tooth to its original anatomy with restorative material, such as silver amalgam. The frusto-conical formation which comprises the larger circlet in FIG. 4 of the matrix 59 is placed upon the tooth as described. The winding member or tool 82 is held in the hand and the fingers operate the knurled section and rotate it in the direction of the arrow as indicated in FIG. 4. Prior to such rotation, the winding member tip 88 is placed into the coil core which it easily seats itself into. The rotation is then initiated and engagement of the winding member inside the coil core is automatic and immediate. The doctor need do nothing specific to cause said engagement; mere rotation is all that is required.

Said rotation causes the rotating or winding coil to draw off all surplus banding material from about the tooth. When all banding material has been drawn off the tooth resistance to rotation begins to develop, the winding tool automatically signals this condition by springing back in the dentists hand. This spring-back action is caused by the tightness of the coil that has just been wound. The spring-back of the coil and the coilwinding tool is a signal to the dentist that he has drawn off all surplus banding material and that a simple rotation of one-fourth turn more will cause an automatic locking mechanism, which is part of the lock-loop 61, to operate and automatically lock the matrix in its tightened adaptation about the tooth. Such adaptation causes the matrix to automatically move gingivally due to the conical formation thereof and thereby seat itself subgingivally into the gingival flap where the dentist desires the matrix to penetrate. The dentist need not do anything in particular to cause the locking mechanism to function, as referred to hereinafter, because such mechanism functions totally automatically.

When said tightness is accomplished, the practioner merely rotates the winding member counterclockwise, that is, in the opposite direction from which he previously wound it tightly, and simultaneously, while such winding is being done, he withdraws the winding member tool from the coil core from which it disengages automatically by such reverse winding, and thereby the dentist is able to remove the entire tool from the mouth. This produces a free field of vision due to such removal of the tool from the mouth. This also readily permits quadrant work for the same reason, because there are no obstructions from retaining tools, which are commonly used to date. Such retaining tools lie over the surfaces of the teeth and prevent the use of more than one matrix in the mouth at a time and even when only one matrix is being used, said matrix retainer lies in the field of vision of the dentist and additionally lies in his work path. For said reasons, such retaining tools are a disadvantage to the dentist. The current and prior patents of this applicant employ the principle that permits the tightening tool to be removed from the matrix and the mouth. After the dentist has plugged the restorative material into the prepared tooth, the work of the matrix is completed. The matrix is then easily opened as follows:

Using a pair of shielded nippers, the top of the lockloop 80 is snipped and cut off and the segment that is so cut remains held under the shield of the clear plastic shielded nippers, thereby preventing said cut segment from entering intra-orally when such cutting is performed. When the lock-loop has been severed, the lock is no longer intact and then, a hooked tool 124 engages hole 38, which is clearly seen in FIGS. 2 and 23. A gentle pull at said hole causes the matrix to spring open. Such easily opened matrices prevent the recently plugged material from being fractured as in the case where conventional matrices cannot be so easily opened as the matrices of the present invention. Once the matrix is opened, it is easily removed from the mouth and the work of the matrix is completed. All of the foregoing procedures require only a matter of seconds to perform.

Details of the various elements of the improved matrix and the functions thereof are described, as follows:

Reference will be made first to the embodiment of the band which is in the form of an improved disposable matrix, as illustrated in the attached drawings.

The disposable matrix illustrated in FIG. 1 is a die cut metal matrix strip, having three portions; a tapered portion 12, a straight portion 14, and an arcuately curved portion 18, all of which comprise the matrix band or strip 10. Strip 10 may be formed of any suitable material, and a preferable material is stainless steel. The stainless steel may be on the order of between 0.0015 to 0.002 inches in thickness and may be inches hard, although other gauges and hardnesses may be used within the spirit of the invention, as well as slight variations thereof will also function properly.

The tapered portion 12 and the straight portion 14 are preformeed into a coil 36 when the matrix is being manufactured. Said preformed coil, or winding portion, is provided to tighten the arcuate portion 18 around a tooth 108. This arcuate portion extends through a predetermined arc, such as, for example, approximately 30 to 40. The arcuate curve 18 terminates at the center of an improved lock-loop holding finger 44 which projects outwardly from said outer arcuate edge 22 of said arcuate portion 18. The end of the finger 44 has a lock-loop engaging notch 42 therein which is disposed between two lock-loop retaining ears 46 and 48 which are for purposes to be described. In alignment with notch 42 of fingers 44 is another notch 40 which is formed in the inner arcuate edge 20 of the arcuate portion 18. The finger notch 42 and the arcuate edge notch 40 function in combination to anchor the lockloop 61 of FIG. 3 onto the matrix band 10 of FIG. 1. The purpose of this will be later described.

Also, for a purpose to be described, a relatively deep and substantially trapezoidal notch 24 is formed in the upper edge 32 of the tapered portion 12 of the matrix band 10, as viewed in FIG. 1, adjacent the terminal end of the tapered portion 12. When the assembled band 59 is supplied to the dentist, it is in the form of a circlet with an improved, reversely wound, preformed coil 36 as seen in FIG. 4.

A conventionally coiled structure comprises a coil which is continuous in a single spiral direction. An example of this is shown in FIG. 5A. The reversely wound coil of the present invention is best shown in FIG. 5B. In FIG. 5B, the tapered section 12 of the band 10 is the reversely wound segment 37 of the preformed coil 36. Advantages provided thereby are set forth below.

Said preformed coil 36 receives a winding member 88, which is enagageable with sloping edge 26 at the end of the tapered portion 12. Said sloped engageable leading edge 26 is disposed within the core 57 of the preformed coil 36 as seen in FIGS. 6, 7, 8 and 9, and

1 1 fully described hereinafter.

The arcuate portion 18 is designed to form a substantially frusto-conical matrix 33 which surrounds the tooth 108 and encircles the same with an inner arcuate edge disposed at the gingival portion of the tooth 108, as seen in FIG. 21. Near finger 44 is a small matrix removing hole 38 which is used to open the assembled matrix 59 for removal purposes when the matrix work is done, as will later be described relative to FIG. 23, wherein a hooked tool 124 is employed to engage the hole 38 for the purposes of opening said matrix 59 as later fully described. As seen in FIG. 1, extending from the outer arcuate edge 18 is the improved finger 44 with its improved ears 46 and 48 and notch 42, which in conjunction with the notch 40 in the inner arcuate edge 20 of the arcuate portion 18, are arranged to hold a lock-loop 16 in position on the matrix band 10 with the finger 44 extending into the lock-loop 61, for such purposes, as seen in FIG. 3.

Referring to FIG. 2, the operation of the ears 46 and 48 of the improved finger 44 and notch 42 will be clear. The ears 46 and 48, finger notch 42, and inner arcuate notch 40, all in combination, hold the lock-loop 61 in position on the arcuate portion 18 of the band 10 and prevents lateral displacement of the lock-loop 61 when the same is placed under working pressures, such as described hereinafter.

Additional means for prevention of lateral movement or displacement of the lock-loop 61 under said applied pressures are also hereinafter described. Additionally to be described is the improved thickness of the lockloop 61 which is two and one-half times thicker than applicants lock-loop covered in his prior patent. The function of such increases thickness is to avoid shearing action of the anchoring notches 40 and 42 and ears 48 and 56 which would render the matrix useless before its usefulness has been accomplished. Such destructive forces occur when the matrix is in the hands of a practioner who had become accustomed to excessive winding of the winding tool from having used matrices that require great torque in order to even partially adapt the same to a tooth. Such a practioner could be considered heavy-handed due to such experiences. Should such a heavy-handed practioner apply such force, it might cause a shearing action to the matrix prior to the fulfillment of its usefulness, as indicated above. However, the improved finger 44 and notches 40 and 42 and the improved, thicker lock-loop 61 all combine to overcome such shearing effect caused by a heavy-handed practioner.

Additionally, the sides of the finger 44 vary in their contour configuration. The inner side 50 of the finger 44 is sloped so as to enable the entry of the coil winding member 88 without any interference from such entry by the finger 44. The opposite side 52 of the finger 44 nearest the terminal end of the arcuate portion 18 is straight-sided. The purpose of the straight-sided formation 52 is to produce a buckling 1 10 of said straight side 52 when the matrix is undergoing the stresses of being adapted to the tooth, as illustrated in FIG. 13. Such buckling 110 on the straight side 52 of finger 44 prevents the lock-loop 61, which is undergoing pressure from a coil-winding operation, from sliding over the ear 48 of finger 44 which would render the matrix assembly 59 unusable prior to having fulfilled its usefulness.

The foregoing condition is one of two situations under which a heavy-handed practioner could cause such aforementioned destuctive action were it not for this automatic buckling 110 that is created while the tightening forces are applied to the band. At the terminal end of the arcuate portion 18, a short tab 54 is provided which is considerably shorter than a similar tab in applicants previous patent and is for the purpose of affording simplified and easy opening of the matrix 59 when its work is done and removal of said matrix from the tooth is undertaken, as later herein described. The second of said two situations referred to above is also described hereinafter.

Initially the improved lock-loop 61 is U-shaped. Referring to FIG. 3, lock-loop 61 includes a straight inner leg 62 having a length equal to the distance between the notch 40 in the arcuate edge 20 of the matrix 10 and the notch 42 of the finger 44, with a bight 66 being formed in the thus far U-shaped lock-loop 61, which engages the arcuate notch 40 of the matrix 10, as shown in FIG. 2. As in FIG. 3, the inner leg 62 is substantially fiat, while the outer leg 64 is formed with longitudinally extending rises or arches a, 70b, and 72. The outer leg 64 is sufficiently longer than the inner leg 62 as to enable the extra length of outer leg 64 to form a bight 68 that bends over the terminal end of leg 62, thereby forming a short leg 78 which overlaps the inner leg 62 and is pressed flat against said inner leg 62 with the finger 44 being sandwiched between said legs 62 and 64, as seen in FIG. 3.

Thus, said overlapping short leg 78 holds the lockloop 61 tightly anchored into the arcuate notch 40 and finger notch 42 of the matrix 10 and thus holds it against any undesirable displacement. The purposes of the rises 70a, 70b, and 72 are the sharp cutting ridges 74 on the outer leg 64 and will be described hereinafter. In should be noted that the applicants prior patent sets forth a lock-loop having two long overlapping flat legs of equal length which were required in order to provide the strength necessary for these thin legs which was required in order to enable the lock-loop to be held in position under applied pressures without being deformed under such pressures. Such overlapping long, flat legs are difiicult to manufacture; however, the new, thicker lock-loop 61 does not require such long overlapping legs, and thus, is eminently easier to manufacture, as well as offering greater ease to the practioner in cutting the same with full assurance that, with the cutting tool supplied, no out segment can possibly fly into the oral cavity. Details of this will also be more fully described hereinafter. A

After the lock-loop 61 is affixed to the arcuate portion 18 of matrix 10, the matrix is formed into the frusto-conical circlet 33 by passing the tapered end 28 of the matrix band 10 through the space between the curved leg 64 and the arcuate matrix section 18 and thereby overlapping the straight portion 14 of the matrix over the arcuate portion 18 of the matrix 10, thereby forming the tooth encompassing frusto-conical circlet 33. Thus, when the straight portion 14 is pulled through said lock-loop 61, as seen in FIG. 4, the overlapping of the straight portion 14 over said arcuate portion 18 forms said frusto-conical circlet 33, as seen in FIGS. 4, 5C, 13, 21 and 22.

To establish the size of the frusto-conical circlet 33, the leading end 28 of the tapered portion 12 is drawn through the lock-loop 61 by pulling said straight portion until the same is fully drawn through the lock-loop 61. The overlying portions of the matrix band 10 which are in flatly slideable relationship with respect to each other are shown in FIG. 5C. Thereafter, both the tapered portion 12 and straight portion 14 are wound into a clockwise coil 36, as seen in FIG. 4, by winding the tapered and straight portions on a mandrel in manufacture, as clearly shown in FIGS. C9. This forms a reversely wound coil of predetermined diameter which is preset by the strut formation 34 which develops from said reverse coiling and is clearly seen in FIGS. 7, 8 and 9..

Such improved method of forming the coil 36 is clearly seen in FIGS. 53 and 5C. It should be noted that the slotted tapered tool 102 of FIGS. 5C and 6 is constructed so that when the slot 105 of the tool 102 straddles the strut 34 of the matrix 10, the slot 105 will be just slightly wider than the strut 34 of the trapezoidal notch 24. The slotted tool 102 is inserted into the trapezoidal slot 24 which lies in the hole of the coil forming fixture 104. When the slotted tool 102 is rotated in the direction of the arrow, the tapered end 28 of the matrix blank 10 winds in the reverse direction from the straight section 14 of the matrix blank 10. This difference in direction forms a sort of S configuration, as seen in FIG. 6. The effect of said reverse winding 37 of FIG. 5B is as follows:

When the slotted tool M12 is rotated clockwise and forms said reverse winding of the tapered portion 12, it, likewise, creates bends 24a and 24b below the trapezoidal notch 24, as seen in FIGS. 5C, 7, 9, 17 and 17A. Said bends establish the length of the strut 34 as seen in said foregoing figures, which therein extends diametrically across the core 57 of the preformed coil 36 and thereby sets the ID. of the coil. Said bends 24a and 24b are formed over the edges of the slot 105 of the tapered tool 102 as said tool is rotated, as herein described and tightened in hole 102 of FIG. 5C. Said taper 107 of tool 192 enables easy removal of tool 1132 from said windings of the completed preformed coil 36, as seen in FIG. 7, which, without said taper, would cause the tool to be bound in the coil. Said slot 105 in tool 102 is of a predetermined width so as to form said bends 24a and 242: at a desirable distance apart and thereby set the strut dimensions at a desirable length to facilitate later engagements of the windin g member 88 in the coil core 57 as hereinafter described.

Such strut 34, with its bends 24a and 24b, defines the diameter of the core 57 regardless of the springiness which develops as the stainless steel is work-hardened while being formed into said coil. Such establishment of a reliable core ID. assures contact and engagement between the coil winding member 88 and the leading edge 26 which lies within the coil core 57. The coil winding member 88 is operated by the practioner or dentist when he introduces the same into said coil core with the tool shown in FIG. 4. Details of the use of such tool are described hereinafter. Briefly, such tool is used for the close adaptation of the matrix to the tooth.

Additionally, the reverse winding also causes the sloping, tapered line 26 adjacent the terminal end 28 of the tapered section 12, to lie within the core 57 of the coil 36. Due to the reverse winding of the coil, the tail of the tapered section 28 lies between the first inner winding and the third inner winding of the coil 36, as shown in FIG. 9. The result of such positioning provides the sloping engageable edge 26 which is somewhat free and clear of the inner winding of the core wall, yet being sufficiently exposed that the winding member 88 of the dental practioner tool 82, as seen in FIG. 4, will instantly engage said edge 26 upon inser- 14 tion into said coil core 57. Said engagement is more clearly defined hereinafter.

The purpose of the tapers 30 and 32 on tapered end 12 shown in FIG. 1 can be clearly appreciated from FIG. 9. Said tapers create conical formations 114 and 116 of the windings at respectively the top and bottom portions of the preformed coil 36. Said inverted conical windings 114 and 116 offer the following advantages. The top inverted conical winding 114 permits easy insertion of the many faceted winding member 88. In applicants previous patent, such inverted conical windings did not exist and the winding tool would catch on the series of coil windings in an attempt to enter the coil core and often inhibited and made coil entry with said winding member difficult in intraoral use, where vision is poor.

The advantage of the bottom inverted conical winding of the coil 36 can best be seen in FIGS. 9, 13, 21 and 22. In applicants prior patent, the windings were formed of straight material and thereby said windings were mways close to the edge of the winding formation. When the praetioner would insert his winding tool, he could cause said windings to cone outwardly and thereby project said rotating windings into the soft gin gival tissue and cause patient discomfort. With the improved inverted bottom cone 116, when such inward pressures are applied, the conical formation moves only within its own windings and does not project into the patients gingival tissue. Thus, no such discomfort to the patient is caused.

The prewound coil 36, as seen in FIG. 8, is manufactured by using the reverse winding procedure shown in FIGS. 5C and 6 which develops the strut formation 34 which establishes desirable core diameter 57 and thus, presets a diameter of the coil core 57 with clearances, for insertion of the coil winding member 88 which is made smaller at the tip than the ID. of the entrance of the coil core 57. This assures entry of the winding member into the coil core 57. The manner in which the winding member 88 cooperates to engage the leading edge 26 of the core 57 is described hereinafter. The matrix is supplied to the dentist in its circlet form and is precoiled as described above and as shown in FIG. 4.

The winding member seen in FIGS. 10, 11 and 12 and the manner in which it engages the leading edge 26 in the coil core 57, as seen in FIG. 13 is described hereinafter.

As previously stated, FIG. 4 demonstrates the fully assembled matrix 59 as the doctor receives it, together with the tool 82 he receives for operating such matrix.

FIGS. 10, 11 and 12 clearly show the design of the winding member and the improvements made upon it over applicants prior patent. As in applicants prior patent, the unidirectional teeth of the winding member 88 are similar. The exceptions between the prior patent and the present invention are as follows: FIG. 10 shows the face of the helic ally arranged flutes on the truncated conical winding member 88 as being smooth and without facets. FIG. 11 shows an alternate truncated conical winding member 89 having straight line rows of flutes with the same smooth face, as in FIG. 12. However, FIG. 12 shows another additional feature, namely chamfered flute ends 94. The flutes are chamfered fully to the root of the flute for the following advantage: Upon entering a preformed coil 36 with the winding member 88 such as used in applicants prior patent, the fluted ends and sharp projections at the truncated tip may make it difficult and cumbersome to insert said winding member into the coil core as said sharp projections on the winding member of applicants prior patent could undesirably hook onto the outermost edges of the preformed windings of the coil, and thus, inhibit entry of said sharp-edged winding member into the coil core. Improvement of the smooth faced truncated winding member 88, together with the chamfered flutes 94, provide a smooth tipped tool that easily enters the coil core 57, especially in combination with the inverted cone 114 now provided in the present coil core. Said inverted cone 114 that developes from the windings offer the equivalent of a countersunk hole so that the winding member 88 actually seeks and seats itself into the coil core 57 by slipping and sliding into said coil core 57 with only the most minor attention being paid to it by the dentist.

As will be noted in FIG. 13, the unidirectional teeth 96 of the winding member 88 are engaging the sloped leading edge 26 within the breakaway drawing Due to the extensive number of unidirectional teeth 96 that approach the leading edge 26 inside said coil core 57, the engagement of said leading edge 26 is almost instantaneous. When the work of tightening is completed, as previously described, and it is desired to remove the tool, the tool is rotated counterclockwise, re versely to the tightening action, and automatically disengages itself from said leading edge 26. The counterclockwise rotation is performed simultaneously with the action of axially withdrawing the tool 82 from the coil core 57. The spring-like quality of the coil 36 which results from the work-hardening incident to being tightly formed causes the coil 36 then to spring open to its original diameter, prior to being tightened and such opening facilitates said disengagement of the winding member 88 from the coil core 57 when such counterclockwise rotation and axial withdrawal is undertaken. The tool is thus easily removed from the coil and from the mouth, leaving the doctor free to operate without any obstructions, such as matrix retaining tools projecting from the mouth.

For a full detailed description of the mechanism of the lock-loop 61, the following is noted: In FIG. 3, the short overlap leg 78 enables the matrix lock-loop to be severed, after the work is done, by using a shielded nippers 118, as seen in FIG. 22, thereby capturing all the cut segments indicated by bracket 80 in FIG. 3 within the enclosed nippers, as shown in FIG. 22 and thus, preventing such cut segments indicated by the bracket 80 in FIG. 3 from objectionably flying freely into the oral cavity due to the cutting action. The remaining uncut U-formation 61' of the lock-loop shown in FIG. 23 remains on the matrix for easy removal by the dentist. Such objectionable free flying of the cut segments would occur if the lock-loop were formed as in applicants prior patent where the segments of the inner leg below the finger center point or cutting line F-F shown in FIG. 21 would be free to fly as they were made of several sections and the U-formation would not be intact as in the present invention. In the prior invention, several segments could fall into the mouth and require the dentist to remove them. In the present invention, all severed segments are caaptured within the transparent shield on the nippers of FIGS. 19 and 22. Said nippers 118, as shown in FIG. 22, have angularly cut safety tips 122 which prevent such nippers 118 from accidentally cutting oral tissue while in the process of cutting the lock-loop 61.

Additionally in reference to the lock-loop 61, as previously noted, the outer leg 64 is formed with longitudinally extending rises or arches, A and 70B. The arches or rises, 70A and 70B, prevent the edges 20 and 22 of the assembled matrix 59 from engaging the edges of the lock-loop 61, thereby preventing shearing of the coil or matrix edges 20 and 22 when the latter is in process of being wound up and tightened. The intersections of central arch 72 with the end arches 70A and 70B form relatively sharp locking ridges 74 which dig into the assembled matrix band 59 as the latter is tightened, thereby preventing retractive movement and loosening of the matrix 59.

The rigidity needed for locking the ridges 74 to dig into the assembled matrix 59, as well as maintaining its full contact with the band, is easily accomplished by the improved thicker aluminum lock-loop 61, which does not deform under the pressures that are applied as in regard to the thinner steel lock-loop of applicants prior patent, which did deform on occasions under the pressures being applied. Such deformations caused ineffective locking. The rigidity of the thick aluminum lockloop 61 overcomes this objection and adds an additional feature of easy cuttability which said aluminum lock-loop 61 affords. The finger 44 extends into the bight 68 of the lock-loop 61 with the notch 42 of the finger engaging inside the bight 68 thereby preventing displacement of the lock-loop 61 laterally relative to the assembled matrix 59. The lock-loop 61 thereby is held at its preset position between the lock-loop 61 and anchoring notches 40 and 42 in the arcuate section of the matrix band 10.

As will be clear from FIGS. 4, 5, 13 and 17, the arcuate section 18 of the matrix band 10 developes a frustoconical, truncated cone formation 33 when the assembled matrix band 59 is applied to a tooth 108, so as to adapt readily to the subgingival 109 of the tooth 108, as shown in FIGS. 13 and 21. Also, the prewound coil 36 is precoiled clockwise, which forms the tightened coil 130 which tightens the assembled matrix 59 on the tooth 108, as seen in FIGS. 13, 16 and 21. FIG. 4 illustrates the band as the dentist receives it and before the tightening is started, whereas FIGS. 13, 16 and 21 illustrate the band after tightening has been completed. Thus, in FIG. 13, the assembled matrix 59 is illustrated as being wrapped around a tooth 108 and extending between a pair of adjacent teeth. The matrix bands just described thus form the assembled matrix 59 that is shown embracing the tooth 108 in FIG. 13.

The aforementioned second advantage of employing the aluminum lock-loop 61 which is two and one-half times thicker than the previous lock-loop employed in applicants prior patent can clearly be seen in FIGS. 16, 17 and 17A, and, in particular, the portion of the as sembled matrix 59 indicated 111 and 112 in FIGS. 17 and 17A. The thicker lock-loop 61 protects the delicate exemplary thin 0.0015 stainless steel material of the assembled matrix band 59 from shearing when subjected to the forces of wrapping same tightly about a tooth 108. Several areas vulnerable to shearing and tearing exist. As in the case of the previously mentioned finger 44, where the bulge is created to protect the ear 48 from shearing, a similar protection is required to protect the ear 56, as seen in FIGS. 17 and 17A.

In FIGS. 17 and 17A the view is from the inner arcuate edge 20 of the assembled matrix 59 on the tooth 108, from the line E-E of FIG. 16. In FIG. 17, portion 111 of assembled matrix 59 is shown as being substantially straight. The partially tightened coil 113 shown in FIG. 17 has been coiled to remove all of the surplus banding material. However, it has not been coiled to a point where the band has become tight upon the tooth 108. In FIG. 17A, the band has been tightened about the tooth by further coil rotation, by using said coil tightening tool 82. Portion 112 of the assembled matrix band is a deformation of portion 111 of said matrix as a direct result of the rotating coil pressing against said portion 111. Said pressure creates said deformed offset shoulder 112 which is maintained in such pressed position against the lock-loop 61 as shown by the arrows in FIG. 17A illustrating that the pressure of the rotating coil prevents the matrix 59 from moving away from the lock-loop.

Said prevention of movement of the portion 112 of matrix 59 away from the lock-loop 61 simultaneously protects portion 56 of the matrix 59 against movement through the lock-loop 61 in which case, should such movement have had occurred, the ear 56 would be sheared off the matrix as ear 56 would have passed through the lock-loop 61. Said offset shoulder 112 can also be seen in FIGS. 16, 23 and 24, which even more clearly illustrate that the offset shoulder 112 protects car 56 from being so torn as it would ordinarily be if it were being drawn through the thinner lock-loop of applicants prior patent. Said offset prevents the ear 56 from being drawn through the lock-loop and accordingly, the shearing does not occur and the force of the dentists hands will not cause any shearing action to take place.

FIG. 23 illustrates the ease and simplicity by which the matrix 59, once it has done its work, can easily and readily be opened and removed from the tooth 108. Once the lock-loop 61 has been cut on line F-F, as shown in FIG. 22, the hook 124 is employed to enter and engage the hole 38 and with a gentle pull, withdraws the notch 40 from the bight 66 of the lock-loop. This operation opens the matrix 59 for ready removal from the tooth 108. Such ease in opening and removal is a positive development in preventing the fracturing of restorations that occur from use of matrices that do not open easily or fully. Most conventional matrices unwind and still are in circular formation during removal, thereby causing a circlet to be removed which, in turn, rubs against the newly formed restoration, often causing it to fracture.

It should be noted that FIG. 23 is an exploded view, showing a dual action in that the severed section of matrix 59, shown on line FF, in actuality, would be caught under the shielded nippers, as shown in FIG. 22. In FIG. 23, the severed section 80 is shown merely to indicate the general area that is severed by the nippers 118. In this view, the offset shoulder that protects the ear 56, previously referred to, is clearly shown. Additionally, the indentations 76 which are caused by the impregnation of the locking ridges 74 into the matrix 59 during the tightening operation are also clearly visible. These indentations 76 form the automatic locking mechanism which will later herein be fully described. Also shown is the terminal portion 54 of matrix 59 and the value of it can be clearly seen in that its short distance from notch 40 permits said short end to be easily slid out laterally from under the lock-loop 61 once said lock-loop 61 has been severed, as shown by arrows in FIG. 23. When said lock-loop is cut, as shown in FIG. 23, the remaining U-shaped configuration 61' remains 18 affixed to the portion of the matrix immediately behind the tightened coil 130, as seen in FIG. 23.

In applicants prior patent, the longer tab at the terminal end of the arcuate curved portion of the matrix was more difficult to disengage from the severed lockloop and such difficulty caused undesirable movement of the matrix, which has, on occasions, fractured the newly formed restoration. The strut formation 34 of the improved matrix 59 is the means by which control of the diameter of the core 57 of the coil 36 is maintained and, in FIG. 17 and FIG. 17A, the strut 34A, being the bottom of the strut fonnation, is clearly visible and also clearly defines the means by which said control is effected. The coil 36, being spring-like in nature, has the tendency to partially unwind after preforming is completed in manufacture. However, due to the strut formation, the ID. of the coil is rigidly controlled by the bent strut which is developed by the reverse winding of the coil 36, such as referred to above. The matrix of applicants prior patent did not employ the reverse coil technique and, subsequently, did not obtain the strut formation 34 and 34A, shown in FIGS. 17 and 17A, which is also clearly seen in FIGS. 7, 8 and 9. FIG. 18 shows how the coil of the matrix was loosely wound in applicants prior patent. It was without a desirable strut and the coil did not have an ID. or O.D. of predeterminable dimensions, as now exists in the present invention. The CD. of the coil of the present invention is set by preforming the coil 36 in hole 106 of the coil-forming fixture 104, as shown in FIG. 5C. The constrictions resulting from preforming said coil in said small hole 106 develop minor kinks in the coil as it is preformed, which sets the desirable relatively tight OD. and ID. dimensions of the coil for ease in inserting winding member 88 into the core 57 of coil 36, as seen in FIG. 8.

Other values derived from such reverse winding are that the leading engageable edge 26, which is now rigidly held in position in the inside wall of the core 57, as seen in FIGS. 7 and 9, is stabilized due to the controlled diameter of the core the new leading edge 26 of portion 12 of the matrix is held in position for ready engagement by the winding member 88 of the dentists tightening tool 82. Formerly, in applicants prior patent, when the coil was wound without the reverse wind 37 being employed, said former winding member would not always reliably engage the spring-like coil core as said spring-like coil, without a stabilized ID. of the coil would expand as the winding member was inserted, and subsequently, the core would be enlarged, thereby causing the former engaging edge, no longer employed in the present invention, to spread open and away from the winding member and thus avoid engagement with said previous winding member.

In applicants prior patent, the sloped edge on the end of the matrix which was engaged by the tool which initially preformed the coil into a continuous spiral winding appears to be similar to slopedengageable edge 26 of the matrix of the present invention. However, there is an entirely different preforming of the coil in both the blanking of the matrix and precoiling of the same. In the prior sturcture, said sloped edge, though innermost in the coil core, sloped and faced in a different direction from the winding member, whereby effective engaging by the winding member was not possible. Instead, a trapezoidal notch was formed adjacent said sloped edge to provide an edge which was intended for engagement by the winding 19 member but, due to the loose coil structure, was not always reliable for such engagement by the winding member.

The object of the said sloped edge at the end of the matrix of applicants prior patent was to afford a gripping means for the pre-coiling tool and was sloped so as not to overlie the trapezoidal notch when the coil was formed, which would otherwise occur and thus the trapezoidal notch would not be exposed for engagement by said former winding member. In said prior patent, the sloped edge did not function as the engageable edge. Instead, the inner edge of the previous trapezoidal notch served as the engageable edge. All this was true when a coil was wound conventionally as in FIG. A, and which was thus not always reliable for engagement by the winding member.

In the present invention, the sloped edge 26 and trapezoidal notch 24 are similar in appearance to the sloped edge and trapezoidal notch in applicants prior patent. However, due to the improved reverse wind of the present invention, the function of the sloped edge 26 and the trapezoidal notch 24, with its strut 34, serve an entirely new function.

In contrast to the foregoing, the new sloping leading edge 26 of matrix in FIG. 1 is set at a predetermined slope of approximately 50to the horizontal plane of the straight portion 14 of the matrix 10 and, in the reverse winding of the coil within fixture 104, the base of the trapezoidal notch forms the strut 34 and controlled OD. and ID. of coil 36 are produced by the new arrangement of said sloping edge 26 disposed within the reverse winding, as described in detail hereinafter, to insure that the leading edge 26 will be held in position for ready engagement with the winding member when it enters said core.

It should be noted that the winding member 88 is conical in shape and, likewise, the trapezoidal notch 24 within the core of the preformed coil 36 is also, in essence, conical in shape. The arrangement of these two conical shapes are as follows: The tip of the winding member 88 is smaller in diameter than the opening of the core 57 of the coil 36, thereby permitting the winding member 88 to easily enter said core 57, as seen in FIG. 8. The winding member 88 is wider than the widest portion of the core 57 of the coil 36 and therefore one portion of the widest part of said winding member 88 will make contact with the inner core 57 of the coil 36 and, particularly, the engaging sloped edge 26 thereof at a point of entry of the winding member 88 into said core 57. Thus, contact is assured between said leading edge 26 within the core 57 and winding member 88 by reason of the differences in the angulation of the conical winding member and the coil core. A clear view of this difference in the diameters of the winding member and the coil core can clearly be seen in FIG. 8.

The foregoing feature of varying diameters between the coil core and the winding member 88 existed in applicants prior patent. However, in the structure of the prior patent, when the coil was wound without the reversed winding 37, which exists in the new matrix as shown in FIGS. 6 and 7, said previously wound coil which was of a springy nature would spread open under the pressure of the entry of the winding member and thereby cause the diameter of the coil core to expand and prevent satisfactory or reliable engagement of the winding member with the prior engageable edge which moved away from said winding member when it was inserted in the core of the coil in said prior patent design.

20 The strut formation 34 that is produced by the reverse winding of the preformed coil of the present invention eliminates such undesirable expansion of the inner core and assures contact between the winding member and the new engageable edge 26 that is employed in the present invention.

Exemplary tightening of assembled matrix band 59 about the tooth 108 is illustrated in FIGS. 13, 14, 15 and 16. Preferably, such tightening is effected by winding the coil 36 against the lock-loop 61, preferably by the tool 82 in FIG. 4, which is covered in applicants prior US. Pat. No. 3,435,905, issued Apr. 1, 1969, entitled, Tool and Method of Manufacturing the Same. As set forth in said tool patent, the tool comprises a palm grip 84 which the dentist grasps in one hand. Furthermore, the tool includes a stiff but bendable core which maintains the annular drive without the necessity of holding the flexible sleeve 126 in any prebent position.

Rotation of the driving sleeve 86 is effected by the dentist grasping the palm grip 84 and using the thumb and forefinger of the same hand to rotate a relatively elongated driving sleeve 86 in a clockwise direction. A flexible coiled sleeve 126 which embraces the bendable core, has one end secured to the driving sleeve 86 for rotation thereby and its other end is anchored to a chuck 128.. A conical winding member 88, as shown in FIGS. 4, 10 and 11, is anchored in the chuck 128 by suitable means, such as solder or the like, as seen in FIG. 13. Thus, when said tool 82 is held in the dentists hand with finger and thumb extending about the driving sleeve 86, and said driving sleeve 86 is rotated clockwise, said driving sleeve 86 transmits and converts the horizontal force of said driving sleeve to a vertical force applied through the flexible sleeve 126 over the bent core and said force is then transmitted to the winding member 88 which is vertical to the driving sleeve 86. Such transmission of force from the horizontal to the vertical, without the use of gears or the like offers the dentist a tool having a low profile and one that does not obscure his vision when using said tool. The spring-like quality of the flexible sleeve 126 offers advantages, hereinafter described, when said tool is used in combination with the assembled matrix 59.

In applying the assembled matrix 59 to a tooth 108, saidmatrix, as shown in FIG. 4, with an oversized circlet, is placed on the tooth. The winding member 88 is inserted into the preformed coil core 5 7 and the driving sleeve 86 of the tool 82 is rotated clockwise. As the winding member 88 is rotated clockwise the abrupt unidirectionally clockwise facing teeth 96 engage the leading edge of the core 57 of coil 36 and begin to wind up the remaining portion of the assembled matrix 59 until the tightened coil wraps itself around the winding member 88 with its ratchet teeth biting into the entire inner core 57 of coil 130. This initial engagement of teeth 96 with leading edge 26 inside coil core 57 and rotating of winding member initiates the development of a strong constricting force of the coil 130 around the winding member 88 which prevents slippage of said winding member 88 inside coil core 57. Such winding of the coil 130 is continued until the coil 130 winds into contact with the lock-loop 61. Further rotation of winding member 88 draws all surplus banding material from about the tooth 108 until the frustoconical circlet 33 is drawn into desired tightness about the tooth 108.

Such surplus matrix material, as it is drawn from about the tooth, forms an ever enlarging coil 130.

When all free surplus has been drawn off, the continuing pull of the winding member 88 begins to stretch the matrix material at the subgingival contact points of the tooth 108, as seen in FIG. 13. This stretching in the stainless steel preferred for the present invention develops a work-hardened condition of the steel at the contact points it makes with the subgingival 134 of the tooth 108, as seen in FIG. 13. This hardening of the arcuate section 18 which encircles the tooth eliminates, by close anatomical adaptation all objectionable spaces between the stretched inner arcuate edge 20 of the matrix 59 and the subgingival area 134 of the tooth 108, thus aiding in preventing objectionable overhang by inhibiting the extrusion of the plugged amalgam.

The automatic lock-loop mechanism which holds the matrix tightly about the tooth 108 during the period of restorative work functions as follows:

The ever enlarging coil 130 draws the surplus banding material from about the tooth 108 through the lockloop 61.. The material so drawn tends to rise up toward the top of the coil, thereby pressing the material upwardiy against and into the impregnating ridges 74 of leg 64 of lock-loop 61, as shown in FIGS. 13, 14 and 15. This continuing interaction incident to the rotation of the winding member 88 and the ever enlarging coil 130 causes increasing upward pressure of matrix material that passes under the lock-loop leg 64 and forces the material to become impregnated onto the sharp locking ridges 74 of leg 64. At the point when all surplus has been withdrawn, further rotation of the winding member is resisted by such lack of material to be so withdrawn, with the following results:

The coil 130 is drawn tightly against the lock-loop 61, as seen in FIG. 14 and a right angle bend 77 develops in that portion of the material which is attempting to rise up to the top of the coil 130, as shown in FIGS. 14 and 17A. At the point where said right angle bend 77 develops, the matrix material is being raised and impaled upon the sharp locking ridges 74 of the lock-loop 61. This action forms impregnations 76 in the rising matrix material, as seen in FIGS. 15, 16 and 23. These indentations 76 develop only at such time as the matrix band 59 is at its maximum tightness. The sharp ridges 74 dig into matrix 59, causing such impregnations 76 to become work-hardened and thus sufficiently rigid to prevent disengagement of impregantions 76 from said ridges 74, thus forming the aforementioned automatic self-locking afforded by said lock-loop 61. This locking mechanism prevents the tightened matrix from loosening under working pressures of plugging and condensing amalgam. The operator or dentist need do nothing special to activate the locking means. The mere rotation of the tool member causes all of the foregoing locking functions to occur automatically, thus rendering the matrix self-locking.

The automatic disengagement of the winding member 88 from the tightened coil 130 occurs as follows:

The previous tight formation of the coil 130 causes it to become spring-like in nature as a result of the workhardening of the materials. To disengage winding member 88 from coil and thus, the entire tool 82 from the coil 130, and subsequently from the mouth, only a single step need be taken by the operator. The operator merely rotates driving sleeve 86 of the tool 82 one-half turn counterclockwise, that is, reversely of the tightening rotation, while simultaneously withdrawing the Winding member 88 and tool 82 axially from the coil core 57. The clockwise rotation releases the unidirectional teeth 96 of the winding member 88, which teeth 96 become released from their bight into the coil core 57 and the engageable edge 26. The spring-like coil 130 opens substantially to its original preformed core diameter size, when the winding member 88 of the tool 82 is rotated in said counterclockwise direction, subsequently freeing contact between the engaageable edge 26, inside the core 57 of coil 130 and the winding member 88, thus, enabling said removal of the winding member 88 from the coil 130 and subsequently from the mouth. The disposition of lock-loop ridges 74 into the impregnations 76 which it had previously formed are in no way disengaged when winding member 88 and tool 82 are removed from the coil 130 and the mouth. The automatic locking caused by said engagement of ridges 74 into impregnations 76 remains intact. Thus, the above condition offers a clear visual field of operation as the matrix 59 remains tightly wound about the tooth 108, as seen in FIG. 21, without the encumbrance of any projecting retainer or other holding device being present to maintain the matrix in place, as is required in conventional matrices.

During the aforementioned adaptation of the matrix 59 to the tooth 108, the pressures being applied in no way cause any destructive action to the matrix 59 as previously referred to. For example, the buckling of the finger 44 at portion 52 causes buckling 110 to act as the preventive means from tearing ear 48 from said finger 44 incident to the tightening action which would otherwise tear said car 48 from the finger 44 were it not for the thickened buckle 110 which prevents the lock-loop 61 from passing over said ear 48 and thus, destroying it. Ear 56 at the gingival arcuate edge 20 of the matrix 59, as seen in FIGS. 16, 17, and 18, is likewise protected against destruction by the rotation of the coil which, as coil 130 is being tightened, it draws tightly up against lock-loop 61 which bears against portion 111, thereby forming the protecting offset shoulder 112, the process of which can be seen in FIGS. 1618. Said offset shoulder 112 stabilizes the ear 56 against undesirable lateral movements toward the lock-loop 61, and thus, prevents ear 56 from being drawn through the lock-loop 61, which would tear or shear said ear 56 from the band, thereby destroying the usefulness of the assembled matrix 59 before its usefulness was accomplished as the assembled matrix 59 would undesirably open prematurely as a result of such shearing.

Inasmuch as the offset soulder 112 is created by the rotating coil 130 pressing against the material 111 which is adjacent the lock-loop 61, all and any continued rotation, regardless of the force employed in the intraoral work that is done only serves to maintain said offset shoulder 112 and thus continues to prevent any destructive tearing action. Hence, the resistance of the offset shoulder 112 to any tearing action is equal to the force of the coil 130 being pressed against said offset shoulder 112. Thus, in essence, a standoff against said destruction is constantly provided. Accordingly, any intraoral overwinding will not cause said shearing, as said overwinding would continue to form said offset shoulder 112, which would prevent said undesirable movements, as described.

The foregoing is equally true relative to the buckle 110 of the finger 44 as seen in FIG. 13. It, too, is affected by such rotational forces which are applied by the coil 130 to the lock-loop 61 which, in turn, is applying forces to said ear 48 which thereby creates the buckle 110. Therefore, continuation of such rotational forces only increases the size of the thickening buckle 110 which is a positive obstacle to further movement of the lock-loop 61 against said car 48. Said prevention of movement of the lock-loop 61 against said ear 48 prevents the destruction or shearing off of said ear 48 by said lock-loop 61. Thus, in two instances, the useof a thicker lock-loop 61 heretofore referred to is significant in creating the anti-tearing devices, (1) to ear 56 of the inner arcuate curve and (2) ear 48 of finger 44.

In both such anti-shearing mechanisms, the present application provides for a thicker lock-loop 61 without which said anti-shearing mechanisms could not exist. In applicants prior patent, a thin lock-loop was employed of the order of 0.10 inch thick. This contrasts with the present 0.025 inch thickness of the lock-loop 61. The prior thinner lock-loop, if used, would have undesirably sheared the ear 48, shown in FIG. 13, as previously described. This is because the ear 48, due to its thinness and the relative sharp edge of said prior thinner lockloop, would have sheared before the buckle 110 could have protected it. This is equally true about the forces applied to the ear 56 on the inner arcuate edge 20 of the matrix 59, as shown in FIG. 16.

Were the prior thinner lock-loop used, said offset shoulder would not develop as the tightening coil would not have a bearing surface to press said material against and thus the offset would not develop in the matrix of said prior patent. In that case, the forces that draw the band against the tooth would pull the ear 56 through the lock-loop, thereby shearing said ear 56 off the matrix 59, at which point the band would open completely and, in essence, would be destroyed before its usefulness would have been accomplished. The thicker lock-loop 61 presently employed and shown in this application positively creates the desired offset shoulder 112 that prevents the movement of ear 56 through the lock-loop and thus prevents its destruction thereby.

After the dental work has been completed on tooth 108, the matrix 59 is easily opened and removed from the tooth 108. Referring to FIGS. 19, 20, 21 and 22, a pair of nippers, which have a transparent shield enclosure 120 is employed to cut the lock-loop 61 along line F-F shown in FIG. 21, and just below the bight of the lock-loop 61 and also below the overlapping leg 78 of said lock-loop 61 in bracketed area 80. The cutting of the lock-loop below said leg 78 by said shielded nippers 118 captures all of the cut segments 80 and retains them in the compartment 120 of the shielded nippers 118 which, when closed, prevents any of said severed or cut segments from flying intraorally from such cutting action. In applicants prior patent, no shielded nipper was employed. Further, the prior lock-loop, when sheared, produced many severed segments above and below the cutting line which dropped intraorally in the mouth. This is highly undesirably for the dentist and patient.

In the current application, the use of the short overlap leg 78 affords the opportunity for the shielded nippers 118 to capture all of the cut segments which are above the cutting line, as seen in FIGS. 22 and 23, as the dentist would desire it to be. The remaining segment of lock-loop 61 that is not cut is in one piece and remains clamped onto the matrix as also shown in FIG. 23, even after the matrix is open. Previously, the cut segments of the lock-loop dispersed intraorally, as indicated in the drawings of the applicants previous patent. This has proven to be an undesirable feature and has been overcome by the formation of the short top lapped leg 78 seen in FIG. 3 in combination with the shielded nippers 118 which cut such segments and retain all of the same within the enclosure 120 of said shielded nippers 118 and are subsequently removed from the mouth in said nipper enclosure. To facilitate the opening of the lock-loop 61, once the segments 80 have been cut therefrom, a hole 38 has been stamped into the matrix 10 near the outer arcuate curve 22, as seen in FIGS. 1, 2 and 23. To open the matrix for removal, a hook tool 124 is inserted into hole 38 and then by pulling at hole 38 with said tool 124, the inner arcuate notch 40 of the matrix 59 is drawn upwardly to become free of the bight 66 of lock-loop 61. Thereafter, opening said matrix 59 is accomplished with a slight lateral movement thereof after the notch 40 has been disengaged from the lock-loop 61. The shortened terminal tab 54 at the end of the arcuate portion 18 thereby requires only said slight lateral movement to disengage entire terminal end 54 from said lock-loop 61. Thereafter, the work-hardened and subsequently spring-like matrix 59 springs open for easy removal without resultant broken marginal ridges of the new, only semi-hardened restoration, such fracturing often resulting from using conventional matrices that do not so easily open for removal from said tooth, as seen in FIG. 23 of this invention. When the matrix 59 and the parts of the lock-loop have completed their work, as previously described, they are discarded and are thus disposable.

Were the matrix 59 in any way made salvagable, so as to remain usable, as shown in alternate designs of applicants prior patent, said current matrix would lose much of its value. The value in cutting the matrix at the end of its work lies in the fact that it opens easily and avoids the fracturing of the restoration produced thereby and previously referred to. Further, a matrix is in its best shape and can make the best restorations, as a retaining wall, when said matrix is new and has not previously been used and thereby deformed, which would offer a poor, irregular retaining wall for the plugged amalgam, and thereby be of lesser value to the dentist. Thus, a good matrix is one of new material and one which has not been deformed from repeated use. Re-use of a matrix also carries the potential of crossinfection between patients.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

I claim:

1. A dental matrix comprising in combination, a strip of thin flexible material having one end portion curved into a loop with an intermediate portion of said strip and overlying the same to form a matrix band, and retaining means to hold said strip in said looped configuration for application around a tooth; said retaining means permitting said intermediate portion of said strip to slide relative to said one end for tightening said band around said tooth, the other end portion of said strip having the edge which is positioned nearest the gingival of a patient being tapered outwardly toward the terminal end for a predetermined distance and the opposite edge of said other end portion also being tapered outwardly toward the terminal end thereof, and said tapered end portion of said strip being precoiled a prede- 25 termined amount, whereby said tapered opposite edges of said end of said strip respectively form a concavity to facilitate the insertion of a coiling tool therein and a concavity in the end of said coil applied nearest the gingival tissue of a patient to minimize possible trauma to the patient.

2. The dental matrix according to claim 1 in which said tapered opposite edge of said strip is more sharply tapered than said first-mentioned edge of said other end portion, thereby to provide a downwardly sloping edge within said socket in said coil to provide effective means to be engaged by a winding tool.

3. A dental matrix comprising in combination, a strip of thin flexible material having one end portion curved into a loop with an intermediate portion of said strip and overlying the same to form a matrix band, and retaining means to hold said strip in said looped configuration for application around a tooth; said retaining means permitting said intermediate portion of said strip to slide relative to said one end for tightening said band around said tooth, a predetermined amount of the outermost portion of said other end portion of said band being pre-coiled to form a socket to receive a winding tool, said retaining means being adapted to be rendered inoperative to permit release of said band from clamped engagement with said tooth, and aperture means in said band adapted to be engaged by an auxiliary tool to facilitate removal of said released band from said tooth.

4. A dental matrix band comprising in combination, a strip of thin flexible material formed into a loop extending from one end thereof and an intermediate portion of said strip flatly and slidably overlying said one end of said strip to form said loop which is adapted to surround a tooth for installation of filling material within a prepared cavity therein, said one end of said strip having a finger projecting laterally from one edge thereof within the plane of said end of the strip, said finger having a notch extending inwardly from the outer end thereof, and a retaining member extending around said one end of said strip and the portion of said strip which overlies it to maintain said loop of said matrix band, a portion of said retaining member extending through said notch in said ear to anchor said member against movement relative to said one end of said strip, and the opposite end portion of said strip being formed into a spiral coil adjacent said retaining member and adapted to be engaged by a coiling tool operable to tighten said loop around a tooth by additionally coiling said opposite end of the strip to draw said overlying portion of said loop past said retaining member.

5. The dental matrix band according to claim 4 in which the opposite edge of said strip from which said finger extends having another notch extending transversely thereinto in transverse alignment with the notch in said finger and said retaining member having a portion also extending through said another notch to facilitate said positioning and retention of said member relative to said strip.

6. The dental matrix band according to claim 4 in which the notch in said finger is disposed intennediately of the width thereof to form a pair of cars respectively disposed on opposite sides of said notch, the finger which is nearest the end of said matrix band upon 26 which the finger is formed having a substantially straight outer side and being of a width adequate to be buckled outwardly due to coiling forces imposed upon said finger by engagement thereof by said winding member and thereby resist being pulled through said retaining member.

7. The dental matrix band according to claim 6 in which the ear on the opposite side of said notch has a downwardly and inwardly sloping outer edge to provide clearance relative to a winding tool when in engagement with the coiled end of said band.

8. The dental matrix band according to claim 4 in which the end of said strip which is adjacent said finger being substantially straight and transverse to the longi tudinal axis of said band and terminating a slight distance past said ear to form a short end portion operable to facilitate removal of a used band from a tooth at the completion of a filling restoration.

9. The dental matrix band according to claim 5 in which said notch in said opposite side of said strip is spaced from the first-mentioned end of said strip a distance adequate to form an ear of sufficient strength to resist tearing and bending when forcefully engaged by said retaining member incident to tightening said matrix band around a tooth.

10. A dental matrix comprising in combination, a

strip of thin flexible material having one end portioncurved into a loop with an intermediate portion of said strip and overlying the same to form a matrix band, and retaining means to hold said strip in said looped configuration for application around a tooth; said retaining means permitting said intermediate portion of said strip to slide relative to said one end for tightening said band around a tooth and said retaining means comprising a lock loop extending around the overlying portions of said strip and formed from a narrow strip of material appreciably thicker than said matrix band, the other end portion of said strip being pre-coiled and positioned adjacent one side of said lock-loop, whereby when said pre-coiled end of said strip is rotated to tighten said strip around a tooth, it bears against the end portion of said strip which extends through said lock-loop and forms an offset shoulder therein adjacent one edge of said lock-loop to resist tearing of strip during such tightening operation, said matrix band further including a finger projecting laterally from one edge of said strip adjacent said first-mentioned end of said strip and said finger having a notch extending inward from the outer end of said finger, said lock-loop extending transversely along one surface of said strip from said finger toward the opposite edge of said strip and sharply around said opposite edge and along the opposite surface of said strip and finger, the terminal end of said lock-loop extending through said notch in said finger and overlapping the other end of said lock-loop for a distance substantially less than the length of said finger, whereby when said overlapping portions of said lock-loop and the outer end portion of said finger are severed and removed to permit removal of said matrix band from a tooth, said removed pieces may readily be trapped within a container on a severing tool and prevented from entry into the oral cavity of a patient. 

1. A dental matrix comprising in combination, a strip of thin flexible material having one end portion curved into a loop with an intermediate portion of said strip and overlying the same to form a matrix band, and retaining means to hold said strip in said looped configuration for application around a tooth; said retaining means permitting said intermediate portion of said strip to slide relative to said one end for tightening said band around said tooth, the other end portion of said strip having the edge which is positioned nearest the gingival of a patient being tapered outwardly toward the terminal end for a predetermined distance and the opposite edge of said other end portion also being tapered outwardly toward the terminal end thereof, and said tapered end portion of said strip being precoiled a predetermined amount, whereby said tapered opposite edges of said end of said strip respectively form a concavity to facilitate the insertion of a coiling tool therein and a concavity in the end of said coil applied nearest the gingival tissue of a patient to minimize possible trauma to the patient.
 2. The dental matrix according to claim 1 in which said tapered opposite edge of said strip is more sharply tapered than said first-mentioned edge of said other end portion, thereby to provide a downwardly sloping edge within said socket in said coil to provide effective means to be engaged by a winding tool.
 3. A dental matrix comprising in combination, a strip of thin flexible material having one end portion curved into a loop with an intermediate portion of said strip and overlying the same to form a matrix band, and retaining means to hold said strip in said looped configuration for application around a tooth; said retaining means permitting said intermediate portion of said strip to slide relative to said one end for tightening said band around said tooth, a predetermined amount of the outermost portion of said other end portion of said band being pre-coiled to form a socket to receive a winding tool, said retaining means being adapted to be rendered inoperative to permit release of said band from clAmped engagement with said tooth, and aperture means in said band adapted to be engaged by an auxiliary tool to facilitate removal of said released band from said tooth.
 4. A dental matrix band comprising in combination, a strip of thin flexible material formed into a loop extending from one end thereof and an intermediate portion of said strip flatly and slidably overlying said one end of said strip to form said loop which is adapted to surround a tooth for installation of filling material within a prepared cavity therein, said one end of said strip having a finger projecting laterally from one edge thereof within the plane of said end of the strip, said finger having a notch extending inwardly from the outer end thereof, and a retaining member extending around said one end of said strip and the portion of said strip which overlies it to maintain said loop of said matrix band, a portion of said retaining member extending through said notch in said ear to anchor said member against movement relative to said one end of said strip, and the opposite end portion of said strip being formed into a spiral coil adjacent said retaining member and adapted to be engaged by a coiling tool operable to tighten said loop around a tooth by additionally coiling said opposite end of the strip to draw said overlying portion of said loop past said retaining member.
 5. The dental matrix band according to claim 4 in which the opposite edge of said strip from which said finger extends having another notch extending transversely thereinto in transverse alignment with the notch in said finger and said retaining member having a portion also extending through said another notch to facilitate said positioning and retention of said member relative to said strip.
 6. The dental matrix band according to claim 4 in which the notch in said finger is disposed intermediately of the width thereof to form a pair of ears respectively disposed on opposite sides of said notch, the finger which is nearest the end of said matrix band upon which the finger is formed having a substantially straight outer side and being of a width adequate to be buckled outwardly due to coiling forces imposed upon said finger by engagement thereof by said winding member and thereby resist being pulled through said retaining member.
 7. The dental matrix band according to claim 6 in which the ear on the opposite side of said notch has a downwardly and inwardly sloping outer edge to provide clearance relative to a winding tool when in engagement with the coiled end of said band.
 8. The dental matrix band according to claim 4 in which the end of said strip which is adjacent said finger being substantially straight and transverse to the longitudinal axis of said band and terminating a slight distance past said ear to form a short end portion operable to facilitate removal of a used band from a tooth at the completion of a filling restoration.
 9. The dental matrix band according to claim 5 in which said notch in said opposite side of said strip is spaced from the first-mentioned end of said strip a distance adequate to form an ear of sufficient strength to resist tearing and bending when forcefully engaged by said retaining member incident to tightening said matrix band around a tooth.
 10. A dental matrix comprising in combination, a strip of thin flexible material having one end portion curved into a loop with an intermediate portion of said strip and overlying the same to form a matrix band, and retaining means to hold said strip in said looped configuration for application around a tooth; said retaining means permitting said intermediate portion of said strip to slide relative to said one end for tightening said band around a tooth and said retaining means comprising a lock loop extending around the overlying portions of said strip and formed from a narrow strip of material appreciably thicker than said matrix band, the other end portion of said strip being pre-coiled and positioned adjacent one side of said lock-loop, whereby when said pre-coiled end of said strip is rotated to tighten said strip around a tooth, it bears against the end portion of said strip which extends through said lock-loop and forms an offset shoulder therein adjacent one edge of said lock-loop to resist tearing of strip during such tightening operation, said matrix band further including a finger projecting laterally from one edge of said strip adjacent said first-mentioned end of said strip and said finger having a notch extending inward from the outer end of said finger, said lock-loop extending transversely along one surface of said strip from said finger toward the opposite edge of said strip and sharply around said opposite edge and along the opposite surface of said strip and finger, the terminal end of said lock-loop extending through said notch in said finger and overlapping the other end of said lock-loop for a distance substantially less than the length of said finger, whereby when said overlapping portions of said lock-loop and the outer end portion of said finger are severed and removed to permit removal of said matrix band from a tooth, said removed pieces may readily be trapped within a container on a severing tool and prevented from entry into the oral cavity of a patient. 